I rebuilt my C4 last fall. I remember one of the servo covers having an o-ring to seal it but the other had a paper gasket. I am finally installing the transmission today. Before I fill it and discover a leak, should I have used gasket sealant on the paper gasket? It was a 'H' servo, and to be honest, the aluminum was pretty deteriorated at one spot. I really don't want to fill this thing and find a leak. I may even swap out the 'H' servo for an 'A' servo I have. Did I mention I really don't want this thing to leak?
Some sealant wouldn't be a bad idea. Changing to a different size servo will probably affect the feel of the shift when that band applies.
Ive had to deal with a few C-4s my self, they really are hard to completely seal up.The areas I had the most trouble with was the bottom pan and around the shift lever rod. I did find the best thing to do on the pan is dont even use the thin paper or rubber gasket the parts store supply, just make sure both surfaces are clean and dry and use a high quaility black silicone sealer, put on a good coating on one of the surfaces, bolt on the pan, but do not tighten completely, just hand tight, give the sealer 5 or ten minutes to start setting up, then use a torque wrench and tighten to req. specs, usually around 60 to 90 inch pounds. On the shifting rod make sure the rod is not worn, or get an o-ring that fits good. A high quality balck silicone sealer, will seal much better than any of those cheap gaskets, when done as stated above. There are high quality re-usable gaskets avalible for most tranny pans, that work great, but I dont know about avalibilty for the C4, at least not at your normal parts stores. On the front and rear seals, I always put a small thin coating of black silicone on the outside of the seals before installation and usually a thin coat of vasoline on the inner rubber seal to ease installation and to protect the seal lip. Hope this helps a little, Im no expert, just the way I do it.
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